The present invention relates to a method of displaying POI (Point of Interest) icons for a navigation apparatus which displays POI icons at places on a map where points of interest are located. More particularly, the invention is directed to a method of displaying POI icons which prevents a POI icon or icons belonging to one POI icon type and appearing in a small number on a map of interest from being hidden behind POI icons belonging to another POI icon type and appearing in a larger number, by depicting the former POI icons after the latter POI icons have been depicted.
A conventional vehicle navigation apparatus reads map data for the area around where a vehicle is traveling from a map storage medium such as a CD-ROM or a DVD by detecting the position of the vehicle, and displays a map surrounding the detected vehicle position based on the read map data. Further, the vehicle navigation apparatus searches a guidance route and depicts the searched route on the map, and also superimposes a vehicle position mark on the present vehicle position which is displayed on the map. As the vehicle moves from its present position, the map is scrolled with the vehicle position mark fixed at a predetermined position on the display screen, and thus a driver can constantly check at a glance a detailed map as well as a guidance route in the area where the vehicle is currently traveling.
Such a conventional navigation apparatus includes a function of displaying an icon or icons belonging to each of three types of points of interest (POI icons) at places on a map where these three types of points of interest are located. These three types of points of interest are selected from points of interest such as an ATM (Automatic Teller Machine), a bank, a gas station, a restaurant, a hotel and a parking lot. This function helps the driver find desired points of interest on the map easily. However, for example, in an area having many restaurants, restaurant icons may conceal behind them a POI icon or icons other than the restaurant icons in some cases, while in an area where there are many hotels, a large number of hotel icons may hide behind them some POI icons other than the hotel icons. Similarly, in a business quarter where there are many banks, POI icons other than bank icons may not be seen if concealed by the bank icons.
FIG. 9 shows an example in which ATM icons, restaurant icons, and gas station icons are depicted in the stated order. In the upper left of the screen, an ATM icon is hidden behind a number of restaurant icons, and in the lower right, a restaurant icon is concealed behind a gas station icon.
Therefore, an object of the present invention is to prevent an icon or icons belonging to an icon type which appear on a map in a smaller number from disappearing behind icons belonging to another icon type which appear on the map in a larger number.
According to the present invention, the above object can be achieved by a method of displaying POI (Point of Interest) icons for a navigation apparatus which displays POI icons at places on a map where points of interest are located, which method comprises: generating POI icon images and overlaying the generated POI icon images in a memory in order of icon type having a larger number of POI icons; and extracting from the memory an image which is as large as a single screen and which corresponds to the vehicle position and displaying such image.
Further, according to the present invention, the above object is achieved by a method of displaying POI icons by which POI icons are displayed at places on a map where points of interest are located, which method comprises: (1) generating a map image using a single unit of map information and writing the generated map image into a video RAM; (2) generating POI icon images and overlaying the generated POI icon images on the map image in a preset order when the total number of POI icons included in the unit of map information is smaller than a preset number; (3) generating POI icon images and overlaying the generated POI icon images on the map image in order of icon type having a larger number of POI icons included in the unit of map information when the total number of POI icons included in the unit of map information is larger than the preset number; and (4) extracting an image from the video RAM which is as large as a single screen and which corresponds to the vehicle position and displaying such image.
Still further, according to the present invention, the above object can be achieved by a method of displaying POI icons by which POI icons are displayed at places on a map where points of interest are located, which method comprises: (1) generating a map image using a single unit of map information and writing the generated map image into a video RAM; (2) dividing the single unit of map information into n segments (where n is an integer equal to or greater than 2), generating POI icon images for each segment in order of icon type having a larger number of POI icons, and overlaying the generated POI icon images on the map image; and (3) extracting an image from the video RAM which is as large as a single screen and which corresponds to the vehicle position and displaying such image.
Still further, according to the present invention, the above object can be achieved by a method of displaying POI icons by which POI icons are displayed at places on a map where points of interest are located, which method comprises: (1) generating a map image using a single unit of map information and writing the generated map image into a video RAM; (2) generating POI icon images and overlaying the generated POI icon images on the map image for a map segment in a preset order when the total number of POI icons included in the segment is smaller than a preset number, the segment being obtained by dividing the single unit of map information into n segments (where n is an integer equal to or greater than 2); (3) generating POI icon images and overlaying the generated POI icon images on the map image in order of icon type having a larger number of POI icons included in the segment when the total number of POI icons included in the segment is larger than the preset number; and (4) extracting an image from the video RAM which is as large as a single screen and which corresponds to a vehicle position and displaying such image.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.